The present invention relates to an image reading apparatus with an automatic document feeder apparatus (ADF) and an image reading method for reading an original transported to a platen. More particularly, the present invention relates to an image reading apparatus and an image reading method that determine whether an original to be read includes black and white images or color images, and read the images on the original according to a result of the determination.
In recent years, a computer, the Internet and electronic photos are widely used to handle color images. Accordingly, there has been an increasing demand for copying, printing, and transmitting the color images because of the superior quality as opposed to black and white images. For that reason, an image reading apparatus has been required to quickly read a color original with high quality.
However, when an image reading apparatus reads a color original, it is normally necessary to read image data for each of the three primary colors, namely red (R), green (G) and blue (B). Thus, when reading a color original with the same resolution as that of a black and white original, the image reading apparatus has to read at a speed slower than for reading a black and white original.
An image reading apparatus may read a set of originals including both color originals and black and white originals. When the apparatus reads such a set of originals in a color reading mode, a speed of reading the black and white originals will be dramatically slowed.
To solve this problem, a conventional apparatus pre-scans an original to determine whether the original has a black and white image or color image. Then, when the original has only a black and white image, the image reading apparatus reads at a comparatively high speed in a black and white mode. Conversely, when the original has a color image, the image reading apparatus uses the color reading mode with a slower speed. This system is known as the ‘pre-scan/actual scan method’.
In Japanese Patent Publication (KOKAI) No. 09-261417, an image processing apparatus has been disclosed as a modified version of the ‘pre-scan/actual scan method’. The reading apparatus is provided with a re-circulating document feeder. It is determined if the original has a black and white image or color image for all documents on the document tray through a process of transporting the originals through a reading position inside the apparatus. Then, the apparatus stores a result for each page of the originals stacked on the original tray. Next, for the actual reading, the originals are returned to the original tray and sequentially fed in the same order. Then, the determination result is retrieved for each original, and the originals are read according to the results based on whether the original has a black and white image or color image.
An image reading apparatus disclosed in U.S. Pat. No. 5,946,527 also employs the pre-scan/actual scan method to determine whether an original is in black and white or in color by reading the original in the process to pass the original on an original tray through a reading position. Then, the original is read again according to a result of the determination.
In the image reading apparatus, it is determined whether the original fed from the original tray includes a black and white image or color image when the original passes through the reading position on the platen. In the image reading apparatus, it is possible to rotate discharge rollers in both directions for discharging the original to the discharge tray. Thus, it is possible to reverse and transport the original to the reading position again, so that both sides of the original can be placed on the reading position.
Therefore, when the original passes through the reading position for the first time, the apparatus determines whether the original has a black and white image or color image. After a leading edge of the original is discharged to the discharge tray, the discharge rollers are rotated in reverse to switchback the original. The original is turned over front to back, so when passing through the reading position for the second time, the apparatus does not read the original. After the original is switched back again on the discharge tray, when the original passes through the reading position for the third time, the image thereupon is read according to the result obtained when the original passes through the reading position for the first time. While the apparatus stores the image data, the original is discharged to the discharge tray.
When the image reading apparatus uses the pre-scan/actual scan method, the same original transport path is used, regardless of a length of the original in the transport direction. Thus, a processing speed is drastically slowed down when the stack contains both black and white and color originals. A short-size original is also transported along a path same as that for a long size original, so that it still takes long time to read the entire original.
In addition to the problems described above, the apparatus disclosed in Japanese Patent Publication (KOKAI) No. 09-261417 has a large size because the original is discharged to the original tray to re-circulate through the tray. Also, it is necessary to provide a memory with a large capacity for storing the results for all the originals in one circulating operation. Furthermore, when the original is jammed during the actual scan, or some of the originals are mistakenly removed from the original tray after completing the first determination scan (pre-scan), an order of the originals is changed and the apparatus uses incorrect results for the actual scan.
The apparatus disclosed in U.S. Pat. No. 5,946,527 employs the pre-scan/actual scan method, and uses the transport path for reading both sides of the original as described above. The apparatus determines a type of original when the original passes through the reading position for the first time (pre-scan) When the original is turned over front to back and passes through the reading position for the second time, the original is not read. When the original is switched back and passes through the reading position for the third time, the apparatus reads the original (actual scan) according to the determination result in the first reading. Therefore, it is necessary to turn over the original without reading it when the original passes through the reading position. Thus, it is difficult to read the color original at a high speed, thereby taking longer to read the original.
In view of the problems associated with the prior art as described above, the first object of the present invention is to provide an original reading apparatus and original reading method capable of determining whether an original includes black and white image or color image when the original is read, thereby making it possible to read the original at a high speed.
The second object of the present invention is to provide an original reading apparatus and original reading method capable of switching an original transport path for an original having a frequently used size, so that it is possible to improve a speed of processing such an original.
The third object of the present invention is to provide an original supply device for supplying a duplex original (an original with images on both sides) and an original reading method of an apparatus provided with the original supply device so that it is possible to process at high speed even when the originals have images on both sides thereof, or include color images on one side or on both sides.
Further objects and advantages of the invention will be apparent from the following description of the invention.